This invention relates to the field of hydraulic transmission systems such as hydraulic pumps, motors, transmissions and torque convertors. More particularly, the invention relates to a fully variable output hydraulic pump.
Typically, variable capacity pumps or motors include reciprocal pumps and single action rotary vane type pumps which are capable of varying the flowrate of hydraulic fluid pumped therethrough. These types of hydraulic pumps are used for pumping oil under pressure for various applications such as power equipment, farm equipment, mobile equipment and other types of equipment where hydraulic motors and cylinders may be used. Typically, the output of the oil of the pump is varied by varying the input power to the pump, thereby varying the rotation of a rotary vane type pump or increasing the rate of reciprocation of a plunger type pump. Also, the pump's capacity can be varied by moving certain parts in relation to other parts. The problem with these pumps when used as transmission systems, torque convertors or motors is that they operate at optimum efficiency only for a narrow range of input speeds.
In order to vary the output of a pump, it is possible to either increase the speed or power input to the pump or increase the pump's volumetric capacity. Variable outlet pumps which operate by varying the pump's volumetric capacity by varying the axial position of rotary gears are known in the art. However, these variable output pumps suffer from certain deficiencies. For example, these pumps often have dead spaces where hydraulic fluid becomes trapped causing a back pressure within the pump which adversely affects pump efficiency. Also, the sealing systems, utilized within the pump are often inadequate causing loss of pump pressure.
It is therefore an object of the present invention to provide a variable output pump which may vary the pump's fluid pumping capacity by varying the axial position of rotary gears thereby increasing the volume of fluid pumped therethrough.
It is a further object of the present invention to provide a fully variable hydraulic pump which may operate at maximum efficiency and provide optimum power throughout a wide range of input power speeds.
It is yet another object of the present invention to provide a fully variable output hydraulic pump which is simplier in design and capable of being manufactured in a cost effective manner.
It is yet another object of the present invention to provide a basic torque conversion or transmission system which employs a fully variable hydraulic pump or motor.
It is yet another object of the present invention to provide a transmission system or torque convertor which employs a fully variable output hydraulic pump or motor which may be suitable for use in vehicles or mobile equipment.